1. Field of the Invention
The invention relates to organopolysiloxane gels having polyether residues, to processes for production thereof and to the use thereof in cosmetic formulations.
2. Description of the Related Art
Organopolysiloxane gels can be produced by crosslinking an unsaturated organopolysiloxane resin with an Si—H-containing organopolysiloxane, also called an Si—H-functional crosslinker, in the presence of a diluent.
Crosslinks are connections between polymer chains in a three-dimensional network. They may be regarded as long-chain branches that are so numerous that a continuous insoluble network or gel is formed.
Organopolysiloxane networks are frequently produced via platinum-catalyzed hydrosilylation reactions. These frequently involve reaction of an Si—H-containing organopolysiloxane and a vinyl-functional organopolysiloxane. An essential prerequisite for the formation of a 3-dimensional network here is that at least one of the two components, the Si—H-containing organopolysiloxane or the vinyl-functional organopolysiloxane, has more than two functionalities per molecule in the average composition.
The platinum-catalyzed hydrosilylation reaction offers the advantage in the formation of organopolysiloxane networks that no by-products are formed, and that linkage sites and network architecture are tightly defined.
The most important reason for the use of organopolysiloxane gels in cosmetic applications is the sensory advantages achieved thereby, more particularly the improvement in the skinfeel of cosmetic formulations. In addition, these organopolysiloxane gels serve as thickeners in cosmetic formulations.
U.S. Pat. No. 6,423,322 B1 and WO 2013/156390 A1 disclose organopolysiloxane gels which can be produced easily by hydrosilylation reaction of a specific vinyl-functional MQ resin with an Si—H-containing organopolysiloxane in the presence of a diluent and a small amount of platinum hydrosilylation catalyst. The resulting gels do not form any threads and can be homogenized easily to give a stable cream or paste. However, a disadvantage of such gels is that they have only low compatibility with polar organic substances, alcohols or water. As a result, such gels are also incapable of absorbing important cosmetic ingredients such as water or glycerol in adequate amounts, and do not show any thickening effect in aqueous or alcoholic mixtures. As a result, such gels are unsuitable or only of limited suitability for the production of water-based or alcohol-based cosmetic products. WO 2013/156390 A1 additionally teaches the addition of an Si—H-containing organopolysiloxane having a particularly low content of Si-bonded hydrogen atoms to improve the skinfeel, particularly advantageous properties being said to be achieved when exclusively an Si—H-containing organopolysiloxane having a particularly low content of Si-bonded hydrogen atoms is used.
EP 1 132 430 A1 discloses organopolysiloxane gels which can be produced by hydrosilylation reaction of a specific vinyl-functional MQ resin and a polyethoxylated or polypropoxylated allyl alcohol with an organopolysiloxane having a high content of Si—H bonds with about 0.5% by weight of silicon-bonded hydrogen atoms, in the presence of decamethylcyclopentasiloxane as a diluent and a small amount of platinum hydrosilylation catalyst. The resulting gels do not form any threads and can be homogenized to give a stable cream or paste. The use of a crosslinker having a high content of Si—H bonds with 0.54% by weight of Si-bonded hydrogen is described as being particularly preferred. The use of a crosslinker of lower functionality in minor amounts is said to be possible.
However, a significant disadvantage of these organopolysiloxane gels is, in particular, that the skinfeel generated is not ideal for cosmetic applications. Because of the relatively high proportion of vinyl-functional MQ resin, such gels are also comparatively costly to produce. Furthermore, it is found that it is not possible to produce suitable gels when linear organopolysiloxanes are used as a diluent. However, linear organopolysiloxanes are gaining increasing significance in cosmetic formulations, since cyclic organopolysiloxanes, as used in the organopolysiloxane gels disclosed in EP 1 132 430 A1, are increasingly being avoided in cosmetic formulations because of their possibly toxic effects.